linux-kernel - [PATCH v3 1/3] regulator: mt6358: Fail probe on unknown chip ID

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Message-ID: <20230913082919.1631287-2-wenst@chromium.org>
Date:   Wed, 13 Sep 2023 16:29:16 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Lee Jones <lee@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Chen-Yu Tsai <wenst@...omium.org>,
        Zhiyong Tao <zhiyong.tao@...iatek.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: [PATCH v3 1/3] regulator: mt6358: Fail probe on unknown chip ID

The MT6358 and MT6366 PMICs, and likely many others from MediaTek, have
a chip ID register, making the chip semi-discoverable.

The driver currently supports two PMICs and expects to be probed on one
or the other. It does not account for incorrect mfd driver entries or
device trees. While these should not happen, if they do, it could be
catastrophic for the device. The driver should be sure the hardware is
what it expects.

Make the driver fail to probe if the chip ID presented is not a known
one.

Suggested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Fixes: f0e3c6261af1 ("regulator: mt6366: Add support for MT6366 regulator")
Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/regulator/mt6358-regulator.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/regulator/mt6358-regulator.c b/drivers/regulator/mt6358-regulator.c
index 120c60d40ed4..935c7ad56c7e 100644
--- a/drivers/regulator/mt6358-regulator.c
+++ b/drivers/regulator/mt6358-regulator.c
@@ -682,12 +682,18 @@ static int mt6358_regulator_probe(struct platform_device *pdev)
 	const struct mt6358_regulator_info *mt6358_info;
 	int i, max_regulator, ret;
 
-	if (mt6397->chip_id == MT6366_CHIP_ID) {
-		max_regulator = MT6366_MAX_REGULATOR;
-		mt6358_info = mt6366_regulators;
-	} else {
+	switch (mt6397->chip_id) {
+	case MT6358_CHIP_ID:
 		max_regulator = MT6358_MAX_REGULATOR;
 		mt6358_info = mt6358_regulators;
+		break;
+	case MT6366_CHIP_ID:
+		max_regulator = MT6366_MAX_REGULATOR;
+		mt6358_info = mt6366_regulators;
+		break;
+	default:
+		dev_err(&pdev->dev, "unsupported chip ID: %d\n", mt6397->chip_id);
+		return -EINVAL;
 	}
 
 	ret = mt6358_sync_vcn33_setting(&pdev->dev);
-- 
2.42.0.283.g2d96d420d3-goog